Nutrition Diagnosis and Scientific Fertilization of Apple Trees
1, the basic concept
1) The source of essential nutrients for fruit trees
The carbon, hydrogen, and oxygen needed for fruit trees come from air and water, and the rest of the elements come from the soil. Therefore, in addition to carbon, hydrogen, and oxygen, plants mainly rely on roots to absorb these nutrients from the soil.
2) The shape of nutrients absorbed by fruit trees
Fruit trees mainly absorb inorganic ions in the soil, such as potassium ions, ammonium ions, nitrate ions, calcium ions, etc.; but can also absorb certain soluble organic substances, such as urea, amino acids, amides, nucleic acids and phosphoglycerate. Fertilizers mainly supply inorganic ionic nutrients, which are easily dissolved in water, and the fertilizer efficiency is fast. Organic fertilizers can supply both ionic nutrients (after decomposition) and some organic nutrients.
3) How the fruit trees absorb nutrients
Crops absorb nutrients in the soil through the roots, but first the roots and nutrients must be in contact, ie nutrients can be absorbed into the roots on the root surface. How can nutrients reach the root surface? One way is to extend the root directly to promote nutrients. This method is usually called interception. The nutrients intercepted by the root system are few; the other is diffusion, in which the nutrients move from low concentrations to high concentrations. When the nutrient concentrations near the roots are higher than the roots, the nutrients spread to the root surface; The pathway is mass flow, which is the flow of plastids, which is caused by the role of leaf transpiration. As transpiration consumes a large amount of water near the root surface, it causes the surrounding water to move toward the root surface, and the nutrients in the water also move to the root surface. The absorption of root nutrients by crops has two processes: active absorption and passive absorption. Passive absorption is a chemical and physical process that does not require energy. For example, nutrients enter cells through diffusion or charge balance; active absorption is a process that requires energy consumption and is selective. Some people think that nutrients pass through passive absorption into free space (between the cell wall and the plasma membrane) and meet a substance called a carrier on the plasma membrane. The carrier contains ionic nutrients in the cytoplasm, and the carrier needs energy to work. of. Just as cars are carriers, cars need gasoline to move around. Therefore, if the plant supplies less energy to the roots, or some conditions affect the respiration of the roots, and the lack of phosphorus, it will affect the plant's absorption of nutrients.
4) Purpose of rational fertilization
Reasonable fertilization is the requirement that fertilization can achieve the following three purposes: 1 fertilization can make plants get high yield and high quality; 2 get the best economic benefits with the least investment; 3 improve soil conditions create a good foundation for high and stable production, that is to use land Combine with the cultivation of land.
5) The main basis for rational fertilization
The object of fertilization is mainly fruit trees. Therefore, fertilization must first consider the nutritional characteristics of fruit trees. The nutrition of various crops is different, and the requirements for nutrition of the same crop at different growth periods are also different. That is to say, different crops or crops have different requirements for the types, quantities, and proportions of nutrient elements at different fertility stages. Cereals and leafy vegetables require much nitrogen, but legumes require less nitrogen. Because they have root nodules, they fix nitrogen in the air. For example, bananas require a lot of potassium, but less phosphorus is needed. Therefore, the nutritional characteristics of crops are the most important basis for fertilization.
Secondly, fertilization is mainly through soil supply to crop nutrition, so the nature of the soil will inevitably affect the effect of fertilization. Therefore, fertilization must also be carried out according to the nature of the soil. The main consideration is the content of each nutrient in the soil, and the ability to retain fertilizer and provide fertilizer. Whether there is obstacle factor, etc.
Again, it is to consider the relationship between climate and fertilization, such as how to fertilize dry or dry seasons, areas and seasons where rainfall is high, and low-temperature and high-temperature seasons. In short, the climate affects the effect of fertilization and fertilization affects the adaptation and utilization of crops to climatic conditions. In addition, fertilization must be considered in conjunction with other agricultural technical measures.
6) Do fertilizer utilization
Fertilizer utilization refers to the percentage of nutrients absorbed by fertilizers in the current season from the fertilized materials. The utilization rate can be obtained by field experiment and indoor chemical analysis according to the following formula:
The absorption of this element in the fertilized area is calculated by subtracting the ratio of the element's medium absorption in the non-fertilized area divided by the total amount of the element in the fertilized material.
In the current management level of cultivation techniques, the utilization rate of chemical fertilizers is roughly in the following ranges: 30-50% for nitrogen fertilizers, 10-15% for phosphate fertilizers, and 40-70% for potash fertilizers.
7) Nutrition critical period, critical value and maximum nutrient efficiency
The critical period and maximum efficiency period of nutrients in fruit trees are most closely related to the effect of fertilization. The critical period of nutrition refers to the requirement for nutrients of fruit trees during a certain growth period, although the number is not large, but if there is a lack or excess or imbalance between nutrient elements, it will have a significant adverse effect on crop growth and development. For most crops, the critical period generally occurs at the beginning of growth, and the critical period of phosphorus appears earlier, followed by nitrogen and potassium later. Therefore, phosphorus fertilizer is often used as a seed fertilizer in production to ensure that sufficient phosphorus is obtained at the beginning of crop growth.
The critical value is when the nutrient in the crop body is lower than a certain concentration, its growth amount or yield is significantly reduced, and shows the symptoms of nutrient deficiency. At this time, the nutrient concentration is called the “critical nutrient valueâ€.
Fertilizers used in different periods have great differences in the effect of increasing yield, and one of them has a good nutritional effect. This period is called the period of maximum nutrient efficiency. That is, the highest economic output was obtained from nutrient units. Maximum efficiency is often consistent with the period when the crop needs the most nutrients.
2. Four laws
1) Equally important law
The essential elements are equally important in the crop body, no matter how many, and the special functions of any one nutrient element cannot be replaced by other elements. This is the same important law and irreplaceable law of nutrient elements.
2) The minimum nutrient law
Fruit trees need to absorb various nutrients for their growth and development. These nutrients, whether they are a large number of elements or trace elements, are equally important. However, limiting the yield and quality of fruit trees is only the nutrient element with the lowest relative content in the soil, and the yield and quality will increase and improve within a certain limit with the increase of this nutrient. In production practice, if we cannot find this limiting factor, even if we continue to provide other nutrients, it is difficult to increase the yield and quality of fruit trees. The use of fertilization to meet the fruit tree needs of this nutrient element, then another nutrient element with the smallest relative content will become an important factor limiting the yield and quality of fruit trees. This is the famous minimum nutrient rate.
The minimum nutrient rate was proposed by the German chemist Libice. He once said that if there is an insufficient nutrient in the soil, or if it is lacking, even if other nutrients are present, the soil will become a barren land. In other words, the factor limiting yield in some soil is one of the most deficient nutrients. The law of minimum nutrients reminds us that when fertilizing we should find out the lack of nutrients that affect the yield of crops, and the relationship between the proper proportions of various nutrients. The minimum nutrient is not fixed, after solving some kind of minimum nutrients, another certain nutrient may rise to the minimum nutrient.
In order to better illustrate the meaning of the minimum nutrient rate, it can be explained by the barrel principle. The productive potential of fruit trees is like a cask that is surrounded by planks of different widths. When the proportion of these planks is appropriate, a bucket of water can be filled. If the length of the planks surrounding the barrel is not the same, then the amount of water in the barrel is limited by the shortest piece of wood, and the amount of water stored in the barrel only increases with the length of the board. . When this plank is lengthened, another shorter plank will become the limiting factor for the capacity of the barrel. The minimum nutrient law means that the yield is limited by the nutrients the fruit trees lack most, and the yield changes with the increase or decrease of the nutrient to a certain extent. In practice, the following points should be mastered: 1. The minimum nutrient means the least relative content of the soil, not the least nutrient content in the soil; 2. The minimum nutrient cannot be replaced with other nutrients, even if other nutrients increase again. More, it can't increase production. 3. The minimum nutrient is changed. It varies with the fruit tree production level and the amount of fertilizer supply. It should be noted that the minimum nutrient rate applies not only to a large number of elements but also to trace elements.
3) Declining returns
The pay-reduction rate was first proposed by European economists Durco and Anderson, and it reflects the relationship between input and output under the same technological conditions. It means that the remuneration received from a certain land increases with the increase of labor and capital invested in the land, but the amount of remuneration per unit of labor or capital decreases as the input increases. For example, in the fertilization, the effect of a certain nutrient is greater when it is insufficient in the soil, but if the application amount of this nutrient is gradually increased, the increase in the yield per unit of nutrients gradually decreases. Therefore, the amount of fertilizer that yields the highest yield is not necessarily the best amount of fertilizer, because the decline in economic benefits will not increase production. So do not blindly increase the amount of fertilizer. Some people estimate based on experiments that the optimum amount of fertilizer is about 5% less than the amount of fertilizer that yields the highest yield.
4) Factor synthesis law
The growth and development of crops are affected by various factors (water, fertilizer, gas, heat, light, and other agricultural technological measures). Only under the premise that the external conditions guarantee the normal growth and development of crops can the full effect of fertilization be exerted. The central meaning of factor comprehensive rate is: Crop yield is the result of the comprehensive effect of various factors that affect the growth and development of crops, but there must be a dominant limiting factor, and crop yield is constrained to a certain extent by this limiting factor. Therefore, fertilization should be coordinated with other agricultural technical measures, and fertilizers should be used in conjunction with each other. For example, the control of fertilizers for water, fertilization and irrigation is very important.
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